Process of and apparatus for making sodium carbonate by ammonia



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' H. FRASOH. PROCESS OF'AND APPARATUS FOR MAKING SODIUM GARBONATE BY AMMONIA..

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H. PRASOH. 'PROCESS UP AND APPARATUS FOR MAKING SODIUM 'CARBONATE BY AMMONIA.

No. 363,952. Patents d May 31, 1887,

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PROCESS OF AND APPARATUS FOR MAKING SODIUM GARBONATB BY AMMONIA. No. 363,952. .1196 Pategted May 31, 1887.

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. 'HQFRASGH. PROCESS OF AND APPARATUS FOR MAKING $ODIUM GARBONATE BY AMMONIA. No. 363,952. I? Patented May-31, 1887.

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H. PRASOH. PROCESS OF AND APPARATUS FOR MAKING SODIUM OARBONATE' BY AMMONIA.

Patented May 31, 1887 l l I l I I l nrllllvlll xxlllllll Mk R lLLIll N,- PETERS, Plmlo-Ulhngnphan Wuhinsmn. D. C.

(No Model.) 9 Sheets-Sheet 7.

. H. PRASGH. PROCESS OF AND APPARATUS FOR MAKING SODIUM GARBONATE BY AMMONIA. A

No 363,952. aten d May 31, 1887."

9 Sheets-Sheet 8.

(No Model.)

H. FRASOH. PROCE$S OF AND APPARATUS FOR MAKING SODIUM GARBONATE BY AMMONIA.

Patented May 31, 1887.

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(No Model.) 9 Sheets-Sheet 9.

H. FRASOH. PROCESS OF AND APPARATUS FOR MAKING SODIUM GARBONATE BY AMMONIA. No. 363,952.

Patent J Pay 31, 1887.

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NITED STATES ATENT F C- HERMAN FRASCH, OE CLEVELAND, OHIO, ASSIGNOR 'IO THE AMERICAN CHEMICAL COMPANY, OF EST BAY CITY, MICHIGAN.

PROCESS OF AND APPARATUS FOR MAKING SODllJM CARBONATF. BY AMMONIA. I

SPECIFICATION forming part of Letters Pater it No. 363,952, dated May 31. 1887.

Application filed October 19. 1882. Serial Kai-1,614. (No model.)

or sodium carbonate from the natural brine of springs or wells, but is applicable to the manufacture of carbonate of soda from other brine or solution of common salt, (sodium chloride.)

The brine or solution of sodium chloride (NaCl) is saturated with ammonia, (NH,,) and the saturated solution is treated with carbonic acid or carbonic dioxide, (OO,,) which, in connection wit-h the ammonia andwater, effects a decomposition of the sodium chloride and the production'of bicarbonate of soda or hydrogen sodium carbonate (HNaCO,,) and of sal-am-' moniac or ammonium chloride, (NH,Cl.) The bicarbonate of soda is separated by filtration from the ammonium chloride which remains in solution. The'ammonia is recovered from the ammonium-chloride solution by distillation with lime (CaO) and reused; The bicarbonate ofsoda is roasted to convert it into carbonate of soda or sodium carbonate, (Na,CO,.)

of processes and apparatus, and also special improvements in the individual processes and apparatus forming part of such system.

Heretofore the several operations have been carried on by successive batches, so to speak.

For example, a given quantity of brine has been saturated with ammonia, this saturated brine emptied into the carbonator, and a fresh quantity treated. In like manner each operation is successively performed on a given quantity or batch of material. In the present invention the operations go on mainly or entirely in a continuous manner, a constant stream of material flowing through the apparatus and undergoing the necessary treatment in its passage. As heretofore carried on, also, the manufacture has been attended with a considerable loss of material or power, which is saved by the present invention.

In the manufacture of soda from naturalbriues the methods of purification heretofore employed have been insufficient for the purpose, and the apparatus has in consequence been liable to become choked with the impurities, (mainly the earthy chlorides, magnesium chloride, and calcium chloride.) In the present invention difficulty from this cause is avoided. The chlorides and other impurities are so entirely removed that there is no interference with the progress of the manufacture. The processes and apparatus forming part of the new and improved system may, for convenience, be considered under separate headings or in sections, as follows:

I. The purification of the brine.This is accomplished by precipitating the impurities and separating the precipitate by filtration under pressure by means of the filter-press,

centrifugal filter, or equivalent apparatus.

As already stated, the main impurities of natural brines are the earthy chlorides. Their precipitation is best effected by treating the brine first with magnesium carbonate, to precipitate the calcium as calcium carbonate, and then, after separation of thelattbnwith sodium carbonate to precipitate the magnesium as magnesium carbonate. This mode of precipitation has advantages over a single precipitation with sodium carbonate, both because the magnesium compound is obtained in a condition better adapted for use, being separate from the calcium compound, atd because the brine is more readily cleared of the precipitate. When sodium carbonate is used, at once a double carbonate of calcium and magnesium forms, which takes a long time to precipitate, and which it is very difficult to get rid of. It is obvious, however, that filtration under pressare may be applied to brine treated at once lowed by sodium carbonate. In case the brine contains iron, it is preferable tofirst preeipi tate it with a small quantity of lime, so that it will not contaminate the precipitated earthy carbonates. q

II. Utilization of the purified brine.-The brine is made to absorb and recover ammonia from nia, the remainder being used first in a washtower as a solvent or wash liquid to recover the ammonia from the waste gases, and afterward added to the larger body of brine beyond the saturator. The recovery of the ammonia from waste gases by the larger body of brine is effected in column-tanks, through which said body passes on its way to the saturator. The same gases are afterward washed with the smaller quantity of brine in what will hereinafter be called the square tower. The brine is or may be used to wash other gases containing ammonia.

III. Saturation of the brine with ammonia. This saturation is effected in a continuous manner by agitating and spraying the current of brine in an atmosphere of ammonia that is constantly renewed. To this end the brine is run through tubes wherein are spraying or agitating devices, and a current of ammonia is passed through said tubes in the opposite direction. The spraying or agitating devices preferred are revolving paddles scoop shaped so as to lift the liquid. The tubes are preferably also set horizontal, and the flow of material is assisted by conveyer flights or wings set obliquely on the paddle shaft. These flights or wings aid the paddles in agitating and spraying the liquid. A cooling medium is employed to carry off the heat generated by the absorption of the ammonia.

IV. Combination of the saturator with ammonia-still, with saturatorcolumn, and with washtower, and the production of circulation through said apparatus.-The inlet for the ammonia into the saturator is connected with the ammonia-still. (Hereinafter described.) The out let is connected with the saturatorcolumn, in which it is passed through a body of the incoming brine, and it is also connected through said column and a pipe with a wash-tower. A vacuum maintained in the top of the washtower causes the circulation of the ammonia. A single vacuum thus relieves the internal pressure in .the still and causes the ammonia to flow through the saturator and saturatorcolumn and to be delivered into the washtower. This tower, which will, for convenience, be called the pipe-tower, is supplied with pure water, and the ammonia taken up is recovered by distillation. The vacuu m is best maintained by means of an ejector or aspirator operated by a steam-jet. M

V. Correcting 0r rectifying the ammoniaterl brine.-The brine, even ifat first saturated with salt, (as it preferably is,) is no longer so when rial.

it leaves the saturator, for it has become weakened through the condensation of water vapor which is carried from the still with the ammonia. In order to restore its strength the brine is passed through a column of solid salt, which it leaves saturated with sodium chloride. In passing through the saturator the brine is made to absorb an excess of ammonia, and even after it leaves the salt column the absorbed ammonia will ordinarily be more than is required to effect the conversion of the dissolved sodium chloride into bicarbonate of soda. The strength in the ammonia is therefore reduced to this proper degree by addition of fresh brine. For this purpose the washbrine, (referred to in Section II,) which contains only a small quantity of ammonia, is used. The vessels in'which' the admixture of the ammoniated and the fresh or wash brine is effected will be hereinafter termed averaging-tanks. This superammoniation of the brine and the subsequent reduction to the standard strength is considered a new and important improvement, so, also, the restoration of the saline strength of the brine after ammoniation. I

VI. Treatment of ammoniated brine with carbonic acid.-The treatment with carbonic acid for effecting the format-ion of bicarbonate of soda, which precipitates, and of ammonium chloride,which goes into solution, is carried on continuously, the apparatus employed being in some respects like the saturator, but differing in others. It is well known that the reactions between the sodium chloride, water, ammonia, and carbonic acid take place best with the carbonic acid under pressure and by means of intimate and repeated contacts of the reagents. In the present invention the best conditions are secured without the numerous high columns heretofore employed, and with a great saving in space, power, time, and mate- The vessels or tubes in which the carbonation of the ammoniated brine and precipitation of the bicarbonate of soda take place are filled to a certain height with the ammoniated brine, (the level being maintained constant by overflow-pipes) and the upper part of the tubes are filled with carbonic acid under pressure. Buckets carried by shafts are revolved in the tubes, being alternately lifted above and carried through the liquid. When they are lifted, they become filled with car.- bonic acid, which they carry down and deliver in the ammoniated brine. A very large number of vessels or tubes connected in series may be employed. The ammoniated brine is allowed to flow in one direction and the carbonic acid in the other through the apparatus.

VII. Production and maintenance of pressure in the carbonating 0r precipitating apparatus.- The carbonic acid is preferably forced into this apparatus by means of compressors operated by steam-jet and acting on the principle of the injector. The outgoing gases from the carbonating or precipitating apparatus are madeto force their way through a column of liquid having a height sufficient to maintain the desired pressure in the carbonating apparatus, and the outlet of the liquid is controlled by an automatic relief-valve loaded to the desired pressure. The column is divided among a series of column-tanks, instead of having it in one vessel. These column-tanks are supplied with the purified brine on its way to the saturator, as described in Section II. The ammonia, which is carried off in greater or less quantities with the outgoing gases, is collected or absorbed by the brine, and so much less quantity is therefore required in the saturator.- These gases pass from the column-tanks to the square wash-tower, (indicated in Section II,) and may then, with very small loss, be allowed to escape.

VIII. Production of carbonic acid.The supply of carbonic acid is mainly derived from the calcination of limestonetcalcium carbonate) in a kiln. The gaseous products from ordinary .limekilns burning coal or wood are very impure, and should undergo a purifying operation before used in the carbonator or precipitatiug apparatus. To obtain the gases in a state fitted for such use without expensive purification, a kiln burning petroleum or hydrocarbon oil,orsimilar clean fuel,is employed. It is not new to burn lime with such fuel, but. it is new to employ it for the production of carbonic acid in the ammonia-soda manufacture, and it is also new to combine with the kiln burning oil the necessary means for controlling production and for collecting the gases. The kiln is arranged so that the carbonic acid is generated in a continuous manner. Besides the limekilu gases, carbonic acid is supplied from roasting the bicarbonate of soda, as hereinafter described.

IX. Combination of carbonic-acid generators with ca'rbonating or precipitating apparatus-and utilization of heat of carbonic gases.As the carbonic-acid and other gases from the limekiln are very hot, and 'as' a high temperature is not desirable in the carbonator or precipitating apparatus, it is necessary to cool the said gases before admission into said apparatus. To effect this, and at the same time utilize the heat of the gases, the latter are forced through fines or pipes of a grainer or apparatus for evaporating brine, so as to precipitate the salt through the heater-'-for' example. ot' the grainer described in my application for graining and crystalli'zing salt, &c., filed August 29, 1882, and numbered 70,569. (Patented May 8, 1883, as No. 277,418.) The gases are further cooled and are deprived of a portion of their moisture by passage through a condensing apparatus. To force the gases through the apparatus, the compressors referred to in Section VII are employed. The carbonic acid from the roasting apparatus is forced by a compressor through a condenser and is delivered into the kiln-gases as they, pass to the carbonating or precipitating apparatus. The condenser collects some ammonia from the carbonic acid. The carbonating or precipitating apparatus is therefore connected with the kiln and roaster through apparatus for compressing, cooling, and drying the gases and for recovering waste energy or material being collected on an-endless traveling belt of' filtering material, whereon it is washed and whereby it is delivered to conveyers which carry it to the roasting apparatus. The filtering-belt travels over an open-work or perforated support, under which a vacuum is maintained. The chloride-of-ammonium solution passes through the belt and its supportand is collected in a tank, called herein the spider tank.

XI. Recovery of ammonia given of at filter and production of 'oaonnin in Zatter.More or less air makes. its way into the tank beneath the filtering belt, wherein the vacuum is main tained. This air carries along with 'itsome ammonia, which is recovered in a wash tower (called herein the iron-tower supplied with fresh water. The vacuum is produced by an aspirator or steanrejector between the filtertank and the bottom of thetower. The washwater is supplied to the ammonia-chloride tank. XII. Roasting of bicarbonate of soda to convert it into carbonate.-T he roasting is performed in a continuous manner. The bicarbonate is carried through flues heated to a high temperature, wherein it is continually'agitated, so as to maintain it in a granular condition, and thus to permit the escape of the moisture and carbonic acid and ammonia. To secure the necessary conveyance and agitation, scooppaddles and conveyor-flights, keyed to a central shaft and arranged to alternate thereon, are employed. The adoptionof these means is the result of a long series of experiments, great difficulty being found in preventing caking of the material, which not only causes imperfect working, but is soon followed by the stoppage of the apparatus. To secure the neccollected in a dusttrap, which issupplied with a current of pure water for absorbing and carrying away the ammonia. The end of the outlet-pipe from the roaster dips below the surface ofthe water in the dust-trap, so that the gases must pass through said water, which collects the dust and absorbs a large partof IIO the ammonia. The water is constantly renewed, and is kept at the same level by means of an overflow. The soda dust and the ammonia are carried on with the water to the still. The carbonieacid and other unabsorbed gases pass on to a compressor, that forces them into the carbonating or precipitating apparatus. Between the compressor and the carbonating or precipitating apparatus is a small surfacecondenser, which removes moisture and any remaining ammonia. The use of the dust-trap not only saves the fine particles, but prevents them from clogging other parts of the apparatus. v

XIV. Conveying, cooling, and packing the carbonate of sotla.-The carbonate of soda leaves the roaster as a dry granular material, very hot, nearly or quite red-hot, in fact. It is conveyed to a packing apparatus of any known or suitable construction by a screw-conveyer, and is cooled during it passage by a waterjacket surrounding said conveyer.

XV. Collection of anmloniated liqnorsfordistiZlation.The receptacle from which the still issupplied will be called the ammonium-chloride tank. Into it the various wash-waters, 810., containing ammonia (excepting always the Wash-brine which is used in the averagingtanks) are pumped. The liquids are the washwater from the pipe-tower, Section IV, the overflow-water from the dust-trap, Section XIII, and the water from the surface condenser, Section XIII. The chloride-of-ammonium solution from the spider-tank below the filter is also pumped thereinto.

XVI. Distillation of cmmoniatcd liqn0rs. The distillation is performed in a continuous manner. The liquors are mixed with milk of lime and flow through one or more still-columns into a boiler, into which steam is admitted. The ammonium chloride is decomposed by the action of the lime and heat (calcium chloride being formed) and the ammoniais expelled by the heat from solution. The ammonia as it escapes is made to heat the incoming liquors,

whereby it is not only cooled,but also deprived of some of the attendant moisture. A condenseris also employed to further cool and dehydrate the ammonia before permitting it to pass to the saturator.

XVII. Utilization of ammonia naturally prescnt in the brine.Some natural brines contain ammonia. This ammonia, in case the brine is to be evaporated for salt, is recovered by boiling the'brine with lime, asjust described, and is utilized in the saturator.

There are many minor points of inventionsuch as particular construct-ion or combination of parts-in the apparatus which form part of the present improvement. alter fully set forth.

The accompanying drawings represent apparatus constructed in accordance with the invention and adapted to use in carrying the improved processes into effect.

Figure l is a vertical section, partly in elevation, of the column-tanks; Fig. 2, a vertical They are hereinlongitudinal section, partly in elevation, of the saturator and is connected washtower (pipe-towerj) Fig. 3, an end view of saturator; Fig. 4:, a cross section and a sectional elevation, on an enlarged scale, of one of the saturator-tubes; Fig. 5, a vertical section of saltcolumn; Fig. 6,avertical longitudinal section, partly in elevation, of the carbonating or precipitating apparatus; Fig. 6, a vertical section of trap to be used in place of the pressurevalve shown in Fig.- 6; Fig. 7, a cross-section of a tube in'said carbonating or precipitating apparatus; Fig. 8, an end view showing a zigzag arrangement of tubes; Fig. 9, a vertical section of carbonic-acid generator or limekiln; Fig. 10, a horizontal section, and Fig. 11, a detail view in sectional eleva ion of the same; Fig. 12, a vertical section of the condenser between the grainers and carbonator or precipitating apparatus; Fig. 13, a vertical longitudinal section, partly in elevation, of the filter or apparatus for collecting the precipitated bicarbonate ofsoda; Fig. 14, an end view, and Fig. 15, a partial cross-section,'ofthe same; Fig. 16, a vertical longitudinal section, partly in elevation, of the roaster and its dust-trap; Fig. 17, avertical cross section of roaster; Fig. 18a vertical longitudinal section ofapparatns for conveying and cooling the carbonate of soda; Fig. 19, a vertical section, partly in-elevation, of the ammonia-still, the view being divided to accommodate the sheet; and Fig. 20, a partial side elevation-of one of the boiL ers forming part of the still. Fig. 21 is a diagram illustrating the whole plant or connected apparatus in plan view.

The column-tanks, Fig. 1, comprise a number of vessels, A A A, each provided with a perforated false bottom, a, a gas-inlet pipe, a, communicating with thespace beneath said false bottom, a gas-outlet pipe, a", communicating with the upper part of the vessel, a

liquid'inlet pipe, a, emptying into the upper part of the vessel, and a liquid-outlet pipe, (1,-

at such distance above the bottom as it is desired to have the liquid stand. The gas-outlet a of the lowermost vessel, A", is connected with the gas-inlet a of the next highest vessel,

A, and thegas-outlet ofthe latter wit-h the gas inlet of the vessel A. The liquid-outlet a of the upper vessel, A. is connected with the liquid-inlet a of the next vessel, A, and the liquid'outlet of this vessel with the next one, The vessels are thus connected in series, so that the liquid and gas will flow through them in opposite directions, the gas being made to pass through the liquid successively in eac vessel.

The liquid introduced into the vessel A will fill that vessel to the height of the outlet-opening, will overflow into the next vessel, A, partially fill it, and overflow into the lower vessel, A and will escape by the outlet a of the latter. The gas introduced by the inlet a of the lowermost vessel will be delivered beneath the perforated false bottom a of that vessel, will bubble up through the liquid therein, be-

ing diffused by the perforations in the false bottom, will pass through'the outlet-pipe a will be delivered below the false bottom'a of the next vessel, A, by the inlet-pipe a thereof, will bubble through theliquid therein, will pass into and through the liquid in the top vessel, A, and will finally escape by the outlet a of the latter. Bends or traps a in the pipes connecting the liquid inlets and outlets prevent the gas from passing through said pipes, and thus from passing through the tubes, without bnbblingthrough the liquid. The pressure required to deliver the gas below the false bottom of the lowest vessel is proportionate to the heights of all the columns added together. The three columns act as one column of triple height in maintaining the pressure in the vessel (carbonating or precipitating apparatus)-connected with the gas-inlet of the lower vessel, and the useful effect of a high column is obtained without the inconveniences attending its use. Moreover, by the division of the column the gas is more thoroughly washed and the soluble matter (ammonia) dissolved out.

The saturator, Figs. 2, 3, 4, comprises a frame, B, a series .of connected tubes, B, a jacketingvessel, B a shaft, B extending, through each tube, a number of scogp -paddles, b, and conveyerflights b on each shaft, a train of gears, b a drivingpulley, 12 a liquid-inlet, b, and a gas-outlet, b for the upper tube, and a gasinlet, b", and liquid-outlet b for the lower tube.

B is a collecting-vessel for receiving the liquid (ammoniated brine) from thesaturator; B the saturatorcolumn through which the liquid (brine) passes on its way to the. saturator, and B the wash-tower (pipe-tower) in which the gas escaping from the saturatorcolumn is washed to recover the ammonia.

The scoop-paddles b and conveyer-flights b are arranged to alternate on the shaft, and are set spirally around the same. The several shafts are connected and revolved by the train of gears If, to which motion is imparted by a belt or pulley, b

The gas (ammonia) admitted by the inlet 11 passes successively through the tubes 13 in the direction of the arrows, Fig. 2. and the liquid (brine) passes in the opposite direction. The liquid is constantly lifted and showered bythe paddles, and the showered liquid, being struck by the paddles and conveyer-flights, is dashed into spray, which spray is advanced bythe action of the conveyer-tlights. Thetubes being filled with an atmosphere of gas, which is constantly being renewed, the absorption of the ammonia is rapid and complete. The liquid (ammoniated brine) is finally collected in the vessel B, and is thence pumped through the salt-column into the averaging-tanks.

The saturator-column B is constructed like one of thecolumn-tanks, Fig. 1, and the gas es caping by the outlet 1) is made to bubble up through the brine in said column. Thelatter not only collects and absorbs ammonia from with aliquid-inlet, b.

the escaping gas, but also maintains a certain pressure of gas in the suturator.

The wash-tower B is or may be of an ordinary or suitable construction; but is preferably a plain pipe filled with coke or similarv material, and provided atthe bottom with a gas inlet, b and liquid-outlet b, and at thetop An aspirator or-ejector, b, is arranged to create a vacuum in the 7 top of the tower. This vacuum is sufficient to cause the circulation of the gasthrough the saturator, saturator-column, and pipe tower In the tower the gas meets the stream of water that trickles over the coke, and'thelast traces of ammonia are absorbed thereby. It will of course be understod that the absorption of ammonia in the saturator and saturator-column' tends to create a vacuum, and that the amount of gas exhausted by the aspiratoror ejector b is very small. The jacketing-vessel B' has an inlet-pipe, b, that delivers the cooling me-' dium (water) at the bottom of the vessel, where theheat of absorption is greatest, and an outlet-pipe, b, that. allows the heated liquid to run off at the top.

Thesalt-column, Fig. 5, comprisesa containing-vessel, 0, having a hopper-mouth, O, for admitting the salt, a valve, 0 for closing said mouth, when required, to prevent escape of ammonia, a perforated false bottom, 0 for the salt to rest upon, a perforated inlet-pipe, G,

for admitting the liquid (ammoniated brine) and spraying it over the salt, and an outletpipe, O ,-for carrying off the liquid. This outlet is provided with a glass tube, for indicating'the level of liquid in the vessel 0.

The averaging-tanks are large receptacles, into which the'superammoniated brine and the fresh brine are pumped or fed by gravity from a higher level. Preferably the fresh brine is delivered into the tanks with and the supply'is regulated by turning cocks in the different pipes, so that a greater or less proportion of fresh brine will be admitted as the liquid in the averaging-tanks shall show an excess or lack of ammonia. The averagingtanks are or may be provided with level-indicators and with a mixing apparatus-such,

for example, as a perforated pipe for delivering compressed air into the liquid to agitate the same. Two or more tanks are preferably used, each being in its turn filled to the proper height and then discharged.

The carbonating or precipitatl ng apparatus, Figs. 6 and 7, comprises a frame, D, a numher of vessels or tubes, D, connected with each other in series by gas-conveying pipes d and liquid-overflow pipes d; and in each vessel or tube a series .of buckets, D, carried by a revolving shaft, D together with suitable inlets and outlets for the gas (carbonic acid) and liquid, (ammoniated brine,) with means for coolingor regulating the temperature in said tubes and with gearing for revolving the shafts.

are bolted at the bottom to arms attached to bosses that are keyed to the shaft, as shown The buckets are preferably cast, and v clearly in Figs. 6 and 7. The gearing shown consists of sprocket-wheels and chains 5 but any other suitable system could be used instead. The precipitating vessels or tubes D are inclosed in a jacket forming part of framev D, and a perforated pipe, (1", is provided, by which water or other suitable liquid may be sprayed on the top vessel or tube and allowed to run over the others, so as to preserve the proper temperature in the interior.

l The liquid to betreated with carbonic acid (ammoniated brine from the averagingtanks) is introduced into the apparatus by the inlet (1 fills the upper vessel or tube D to the height of the overflow (1, then runs into the next vessel or tube, overflows into the next, and so on, till finally it escapes through the overflowpipe d of the bottom vessel or tube. The gas (carbonic acid) is introduced under pressure into the bottom vessel or tube D by the inlet (P and fills the several vessels or tubes above the liquid. The shafts B revolve so as to carry the buckets mouth forward, as indicated by the arrow, Fig. 7. As the buckets revolve they carry down in their descent the carbonic acid, which they deliver below the surface of the liquid. They then become filled with liquid,which, as they rise, they lift and then pour out through the atmosphere of carbonic acid. Thus they bring the compressed carbonic acid repeatedly into intimate contacts with the ammoniated brine, and the result is the decomposition of the sodium chloride and the formation of ammonium chloride and bicarbonate of soda.

The decomposition of the salt (sodium chloride) and precipitation of the bicarbonate begin in the upper vessel or tube and continue in the others, becoming practically complete by the time the lowermost vessel is reached. The gas is allowed to escape through the col umn-tanks, Fig.1, which maintain the desired pressure in the precipitating vessels or tubes D, while permitting a continuous flow. It is obvious that the pressure is maintained in all the vessels or tubes equally, no matter how many of them there inay be, and no extra power is therefore required to compress the gas anew for each vessel or tube. Twenty to twenty-five of the precipitating vessels or tubes can be connected in series without any difficulty, and experience has shown the ab-' sorbing of carbonic acid so complete that the carbonic acid in the exit gases (after passing through the tubes) may be reduced from one per cent. to one and one-half per cent. instead of ten percent. or more, as has commonly been the case heretofore.

The gas in passing takes up ammonia from the liquid, but it takes up most from the tube it-first meets-to wit, the lowest tube in which precipitation is practically completeand the abstraction of ammonia from it does no harm but will,on the contrary diminish the possible loss of ammonia during the subsequent filtration. The size of the vessels or tubes D is such as admits of a ready control of the temperature at the point found most advantageous. lVater or other suitable liquid at a suitable temperature is distributed by the perforated pipe d over the top vessel or tube, flows over its exterior to the next vessel or tube, and so on over each vessel, until it'finally escapes by the outlet (1.

The ammoniated brine is pumped into the precipitating vessels or tubes D against the pressure of the contained carbonic-acid gas. The outlet for the ammonium-chloride solution holding the precipitated bicarbonate of soda in suspension is controlled by an automatic relief-valve, D*, of ordinary construction, which is properly loaded so as to permit the said solution and precipitate to flow away without disturbing the conditions of pressure in the apparatus.

Instead of a relief-valve, the trap shown in Fig. 6 may with advantage be employed. It may be considered,generally, as a U orsiphon trap having legs of sufficient length to maintain the pressure in the precipitating apparatus, and provided with stirrers to prevent the bicarbonate from settling. The inclosingvessel D, which forms the descending leg of the siphon, is provided with a screw or propeller, d, carried by a vertical shaft, d and placed near the bottom of the vessel. The pipe D, which forms the ascending leg, is provided with an upright stirrer, D, the shaft of which is stepped in a skeleton frame, d", at the bottom of said pipe D. r

In Fig. 8 the precipitating tubes or vessels Dare arranged in a zigzag instead of in a vertical line, whereby a larger number can be placed in the same height.

Since the overflow-pipes d are no longer vertical, there is greater liability of the precipitated bicarbonate clogging the tubes, and it is advisable, therefore,to provide each ovcrflow-pipe d with a stirrer like that illustrated in Fig. 6* and lettered D, the said stirrer being, however, inclined to correspond with the position of the overflow-pipe in which it is placed. Each vessel or tube is shown provided with a perforated pipe, d", for distributing water over it. The water is collected by inclined shelves d ,and carried off by troughs at the bottom thereof.

The carbonic-acid generator or limekiln,

Figs. 9,10, and 11', comprises, in connect-ion with a number of atomizers, E, a shaft, F, provided at the top with flues E,for collecting and carrying offthe carbonic acid, and also with a direct out-let, E and a removable cover, E, therefor,and terminating at the bottom in an in verted cone, E, the contracted mouth of which has a grating. ,on which theline may rest. The atomizers Eare placed so as to deliver the fuel (petroleum or hydrocarbon oils) into the shaft F just above the cone E. Each atomizer comprises an oil-receptacle, e, an oil-delivery tube, 6, and a steam-pipe, e". The oil-tube e and the steam-pipe e extend through the wall of the shaft F. The outside portion of the ,oiltube is bent downward, so as to extend into port combustion enters through the grate j. Connected with the flues are the compressors, in the form of injectors,fwhich take the gas from the flue E, force it through the grai ners and condensers,(shown in Fig. 12,) and delivers it in a compressed state into the carbonator or precipitating apparatus, Figs. 6 and 7 or Fig. 8. t

The action of the compressors during operation gives ordinarily sufficient control over the draft of the kiln; but a valve,f, sliding n guldes below the grate f, is also provided as an additional or auxiliary means of regulation or means to be used when the compressors are not inaction. The cover E is removed to fill the shaft with limestone and to supply additional limestone from time to time. The lime is removed from the bottom,as required, by removing one of the grate-bars. The grate is sufficiently elevated to allow a car for receiving the lime to be run beneath it. During operation the fuel delivered in regulated quantity isdistributed allover the base ofthe shaft, so that all parts of the limestone are equally calcined. By regulating the draft the best temperature for Working can be readily secured, and the supply of carbonic acid generated can be kept within the desired limits. The grainers may be of any ordinary or suitable construction, butare preferably such as de scribed in my application already referred to.

The condenser, Fig. 12, through which the carbonic acid is passed on its way from the kiln to the carbonating or precipitating apparatus resembles a still-column in construction. It comprises a shell, G, divided by perforated diaphragms G, and having overflow-tubes G for conducting'the condensing liquid from one diaphragm to the next. The liquidifiletg and gas outlet 9 are at the top of the shell, the gas inlet g' and the liquid-outlet g at thebottom. Thegas (carbonic acid from limekiln) is forced into the shell G at gfland passes up through the perforated diaphragm G and out at the top. The liquid (water) for cooling the gasand condensing the moisture therein,being introduced at g, descends from diaphragm to diaphragm by the overflow-tubes Giand, being prevented by the pressure of the rising gas from passing through the perforations, collects to a certain depth, regulated by the height of the overflowtubes.

dip into cups g, which become filled with water and prevent the gas escaping up the said tubes. The gas in passing through the perforated diaphragm and the layers of water thereon becomes cooled and deprived, in part at least, of its moisture. The gas in the condenser being under pressure, it is necessary to control trough shape.

The lower ends of the overflow-tubesv the outflow of liquid. For this purpose the liquid-outlet g is connected with a trap, H, having two long but unequal legs, h h. The longerleg, h, projects above the-outlet g or top of the shorter leg, h,to such a distance that the liquid therein will about balance the least normal pressure in the lower part of thecondenser. The entire length ofthe longer leg is such that thepressureof theliquid therein will always be greater than the pressure in the condenser. Variations in pressure in the condenser willv therefore cause the liquid to rise and fall in the shorter leg, and the trap will automatically adapt itself to such variations and continue to operate. It will never blow out, because the pressure will be insufficient to balance the column in the longer leg, h, except when the shorter leg, is wholly or partly filled with liquid. *In the longer leg, h, at or about the level of the outlet 9 a stop-cock, H, is placed, so that the liquid may be drawn off from the higher portion of the longer leg and A be blown off from the V-shaped part of the trap. H is a waste-water funnel and pipe.

The filter, Figs. 13, 14, and 15, by which the precipitated bicarbonate of soda is separated from the ammoniumchloride solution, comprises a filter-tanl ,K,an endless filter-belt, K, and drums K, for supporting the belt, together with various accessory parts. The drums K are journaled i-n hearings in a framework and the filter-belt, which runs thereon and is moved by power applied to one or both drums, passes over the top ofthe filter-tank K, the said tank being placed between the drums, and has its top formed of rollers k, to diminish friction on the belt and to allow the filtered liquid to fall into the tank. is a trough formed by the side pieces, In, the bottom of the trough being the top of the tank. Thetrough is somewhat narrower than the filtjerbelt, and at the front (left hand) ends of the side piece are turning-up devices 7c, (shaped something like plowshares,) which raise the edges of the belt and give to it a- (See Fig 15.) A flap, k of stiff rubber, fits within the folded belt and prevents the liquid which is introduced by the pipe 10* from running out, but does not interfere with the movement of the belt, which is in the direction of the arrows. Thetrough is closed by a cover, 70 An atomizer, L, is arranged with the jetopenings inside the cover in position to spray water over and to wash the bicarbonate on the filter-belt. A hinged evening device, L, distributes the bicarbonate evenly over the bottom 'of the trough. A vacuum is maintained under the filter-belt to assist the percolation ofthe liquid. The tank K is divided bypartitious k into a number of compartmentsyeach connected by-an individual branch pipe, 70', having a cock, 70 and a common pipe, k", with an aspirator and compressor, K This aspirator 5 Above the tank and compressor create a vacuum in the filtertank below the filter-belt, and the air or gas ate and delivers it into a conveyer, L.

withdrawn is forced into a wash tower to recover the ammonia therefrom. The object of having an individual branch pipe and cock for each compartment is to enable the vacuum to be independently controlled, so that different degrees of vacuum may be maintained therein. Over the first or left-hand compartment the liquid is deeper and the vacuum in the compartment beneath is kept correspondingly large, while there-is only a very shallow layer of liquid, or none at all, over the righthand compartment, and a small degree only of vacuum is requisite. Each compartment of the tank is also connected by an individual branch pipe, k having a stop-cock, k, with the common pipe k, leading to a tank which collects the filtered liquid. (ammonium-chloride solution.) The pipe 76 is connected with this tank, so that the pressure therein is relieved and does not interfere with the flow of liquid from the filter-tank. I

The filter-belt carries the washed bicarbon- Scrap= ers L detach the bicarbonate which does not fall off of itself. The filter-belt is purposely left rather loose. One or more frictionpulleys such as shown at L*are used to prevent slipplng on the drums. Said pulley, which is faced with rubber, has sliding journals, and is pressed by screws Z against the belt, so as to clamp it between itself and the drum. Slipplug is. thus prevented without tightening the filter-belt.

The roaster, Figs. 16 and -1'7, comprises, mainly, a series of fines, M, set in a furnace, M,-and provided with internal agitating and conveying devices, M M The agitating devices are scoop-shaped paddles M and they are arranged on shafts M alternately with the conveying devices or flights M The shafts are driven from a power shaft, "m, by means of chains and sprocket-wheels. The material to be roasted (bicarbonate of soda) is. introduced by the hopper m, and the roasted material (sodium carbonate) is delivered at the outlet m. Both the hoppers mouth and the outlet are protected by loaded fiap-valves m for excluding air, while permitting the introduction and discharge of the material.

The furnace M, as shown, is divided into several fire-chambers, each having its own fire-place n and discharge-flue n, the dischargeflues delivering their products, however, into a common chimney or uptake.

The fines M, being placed in the fire-chambers, are exposed to the full heat of the fire, and, being surrounded by the products of combustion before they have a chance to cool and by being also exposed to direct radiation, are highly heated. The heat expels the extra equivalent of carbonic acid, also the moisture and ammonia. The conveyer-flights propel the material through the flues and the paddles lift the bicarbonate and throw it over the fines, and thus insure that all parts are equally roasted. The paddles also keep the mass in a granular condition, which permits the easy escape of the gases to be driven off. The paddles are of the utmost importance, as ascrew alone would roll and ball the soda, and the latter would collect in lumps fused on the outside and containinginside ammonia, moisture, and carbonic acid.

\Vith the apparatus described a fine powder is produced perfectly free from ammonia and moisture. The expelled products are carried 01f by the pipe a the outer end of which dips below the surface of the water in the dusttrap N. The gases pass out by the pipen to the compressor, which forces them into the carbonating or precipitating apparatus, on their way to which they pass through a surface-condenser that condenses more or less of the moisture and recovers the ammonia which dissolves in the condensed water. The water in the dust-trap is constantly renewed through the pipe a. i The water collects the soda dust which may be carried out of the roaster by the gases, and also dissolves a portion of the ammonia. The-water escapes by the over- The sodium carbonate leaves the roaster by the outlet at in the form of a fine dry powder, which is very hot. In the upper fines the temperature is kept low by evaporation or vaporization which takes place. therein; but in the lower flues but little evaporation or vaporization takes place,and consequently the sodium carbonate is delivered of a temperature nearly equal to that of the fire-chamber. To convey it.the apparatus shown in Fig. 18 is employed. This consists, mainly, of a screw'-conveyer,P, provided with a water-jacket, P,whereby the soda is cooled in its passage. The couveyer P being at a higher level than the outlet of the roaster, an elevator, P, is employed to raise the material and deliver it into the conveyor. The elevator should bewholly of metal, or,at least, it should contain no inflammable material or material likely to be destroyed by the high temperature of the powder. The conveyer delivers the cooled carbonate of soda to packing apparatus of ordinary or suitable construction, which packs it in barrels or other receptacles.

The still. Figs. 19 and 20, receives the ammonium -chloride solution from the filter, Fig. 13, also the water from the pipe-tower, Fig. 2, from the iron tower, from the dusttrap, Fig. 16, and from the surface coudenser, these liquids being first collected in the ammonium-chloride tank.

As shown, the still proper comprises thetwo columns Q Q and the two boilers R R, with their appendages. In connection with them are the small auxiliary condensing-column Q, for cooling the ammonia and heating the incomingliquid,the condcnser-coilQ for further cooling the ammonia and depriving it of moisture, the lime-tank S, for mixing the ammoniacal liquor with milk oflime,and the mixing apparatus S.

The still-columns Q Q are alike, and com: prise each a hollow column of irregular form inclosed in a shell or casing.- The hollow column is formed of a number of communicating vessels, q, of a general hemispherical shape, fitted and held together by a bolt, q, the fiat sides being uppermost. The lowest vessel q basin the bottomholes through which communication is established between the interior of the hollow column and that of the inclosing casing or shell q. Surrounding each vessel q, (except the top and bottom ones,-)and resting upon the vessel (1 next in order below. are frusto-conical drip plates ithe object ofwhich is to direct upon the fiat top of the next vessel q the liquid which may fall on said plates. The ammoniacal liquid to be distilled is admitted into the shell q of the column Q by the pipe q,flows over the exterior of the vessels q therein,passes the siphon-pipe Q5 into the shell of the columnQQfiows over theexterior of the vessels therein, and finally runs out by the pipe q,and is delivered into one ofthe boilers R R.

From thetop of the shell q" of column Q the steam and hot ammonia vapor pass by thepipe g into the top vessel 9 of column Q,;- theuce they descend'through the interior of vessels q and cscapeat the bottom into the shell g of column Q. The steam and ammonia thence escape by pipe into the condenser-column Q of which more will be said hereinafter. The boilers R R are both plain cylinders. They are provided each (see Fig. 20) with a steam inlet pipe, 1'1", extending thelength of the cylinder and perforated at intervals, also-with a blow-off pipe and cock, 7*, with a steam and vapor outlet, 1%, and with a liquid-inlet pipe, 1' 1". The steam inlet pipes rrare connected with a common steam-pipe, s, and are provided each with a cock, 8 8 respectively,

whereby steam can be shut off or let on to each boiler independently. There are also cross connection-pipes rFr between the steam inlet pipes 1* 1" and the steam and vapor outlets 1' 1, respectively, and each cross-pipe has a cock, s s", respectively.

The steam and vapor outlet-pipes 1' 1- are connected with the pipe (1 and have each a cock, 3 s, respectively. By properly opening and closing the cooks the steam from pipe 8 can be admitted into either boiler. Then, with any ammonia vapor generated, it can be passed into the second boiler, and thence into the still-columns, or it can be passed directly into the still-columns without passing through the second boiler, or the steam can be passed through both boilers simultaneously, or the steam can be admitted directly into the stillcolumns without passing through either boiler.

For example, by closing cocks s s s and opening cocks s, s", and s", the steam from is will pass through 1', R, 1' 1", 1*, R, i and g to column Q. By closing cocks s s and opening cocks 8 (leaving 8 8 closed and 8 open) the route is the same, omittingi' r, R, and r, the steam thus passing directly from pipe 7' into the pipe if. By opening cocks s s" s s and closings s steam from pipe 8 will pass into both boilers R R, and thence by the outlets 1' r to the pipe 9 Theliquid-inletpipcsrr are connected with the pipe g, leading from the still-column Q, and they have each a cock, s 8 respectively, whereby the liquid can be directed into either of the boilers or be allowed to flow into both. Ordinarily the liquid from the still-column is allowed to fiow into one -boilersay R while the steam. is passing from pipe 8 into the other-say R. the latter pass into the first .boiler, R, thence to the still-column Q. When the ammonia is all driven olf from the liquid inboiler R, itis cut off by closing cocks s 8 (s s 8 being al- The steam and vapor from ready closed,)' and the liquid is blown off through the cock 1*. ,The exit can be assisted with steam from pipe s, if desired.

During blowing off the steam is admitted into boiler R, and passes thence directly into still-column. cock 8 is closed and cock 8 opened, so that the ammoniacal liquid runs into the boiler R. The cock 8 is also opened and-the cock 8 closed, so that the steam and vaporfrom boiler R now pass through boiler It, and thence to the still-column. When the liquid in boiler R is exhausted, this boiler is blown off and When boiler R is empty, the

IOO

the cocks are opened and closed to effect the 9, is slaked in tubs close to said generator or kiln, and the milk of lime is: delivered by means of monte-j us (such as commonly 'employed in sugar-works) into "the mixing apparatus, which keeps a constant supply ready for delivery into thelime-tank S. As shown, the milk of lime is delivered through the pipe t and the flow is regulated by the cock 1;; but it is preferred to place a measuring-elevator between the mixing apparatus and the limetank, so as accurately to regulate the delivery. More than one mixing apparatus can be used.

The lime-tank S is a horizontal cylinder, in which is centrally mounted a shaft, a, provided with stirrer-frames a. Two such frames will answer; but a larger number can be used, if desired. The shaft is revolved by a belt on pulley a, or by other appropriate gearing. The ammoniacal solution is delivered from the condenser-column Q by the pipett and passes into the still-column Q by the pipe g*.

The condenser-column Q is not, per se, of novel construction. It consists of the upright l'lO shell 0, perforated diaphragms o, overflow-' at B2.)

inlet pipe q is provided with a cap, 1)", which prevents the liquid from running through said pipe into the still-column. In the condensercolumn the steam and hot vapor from the still-columns meet the incoming ammoniacal liquor (which is delivered in measured quantities through the pipe 0 and parts with its heat thereto, so that the said liquor is hot when it enters the lime-tank S, wherein the decomposition of the ammonium chloride by the lime is effected. The lime-tank S may be heated by outside agencies, if desired; but this ordinarily is not necessary. In the condenser-column, also, the steam is condensed and the ammonia vapor partly deprived of moisture, both by contact with the liquid and by passing through the holes in the dia phragms v. p

The condensercoil Q is a simple coil combined with a perforated pipe, 0", for spraying cold water or other cooling liquid over it.

Having now described the various apparatus employed, and having explained their operation, it remains to give a short description of the operation of the system as a whole. Reference will be made principally to Fig. 21, which is lettered, as far as possible, to correspond with the other figures. The dotted arrows indicate the ilow of gases. The solid arrows indicate the flow of liquid, except the feathered arrow in the lower right-hand corner, which indicates the passage of solid can bonate of sodium.

Assuming that the brine to be treated is on containing ammonia, with impurities of ironcompounds and earthy chlorides,the said brine, as it comes from the springs or wells, is treated with a small quantity of lime, sufiicient to precipitate the iron, and a small quantity of magnesia. This crude or slightly-purified brine is pumped into the tank U, from which the other apparatus are supplied. The brine to be evaporated for salt is run by the pipe 100 into the lime-tank \V, wherein it is mixed with milk of lime from the mixer and run into a still Y, and the ammonia being driven off is collected and conveyed through the condenser Y and pipe 101 to the saturator, (indicated The brine is then pumped into the grainers, which are heated by the kiln-gases on their way to the earbonating or precipitating apparatus. The gases from the kiln F (shown in detail in Figs. 9,10, and 11) are by the compressor F forced through the heating-coil 102 of the grainer, and thence pass by the pipe 9 into the condenser-column G, (shown in detailin Fig. 12,) wherein they are cooled and washed by water from the tank 103, which Water is introduced by the pipe 9 and runs away by the pipe 11. The gases enter the carbonator D (see Figs. 6, 8) by way of the pipes g d. The brinefor sodamaking is run from the supply-tank U into a tank, 104, where it is mixed with magnesium carbonate, preferably with the fresh]y-precipitated carbonate from the filter-press. The quantity of magnesium carbonate used is that required to decompose the calcium chloride in the brine. From the mixing-tank 104 the liquid runs into a settling-tank, 105. After settling for, say, twenty-four hours, the clear liquor is decanted into a miXing-tank,106, where it is mixed with sodium carbonate in quantity sufficient to de compose the magnesium chloride and a slight excess, and is then run into a filter-press, 107, of ordinary or suitable construction, or into a centrifugal filter or other apparatus for filtering under pressure. In this press magnesium carbonate is retained and the clear bright brine is run oil". The magnesium carbonate contains not only the natural magnesium of the brine, but the quantity added to precipitate the calcium. It can be sold or utilized in any desirable way. There aretwo mixingtanks, 104., two settling-tanks, 105, and two mixing-tanks, 106. They are connected by pipes arranged, as indicated in the diagram, (thepipes being provided with cocks,) so that either of the settling-tanks 105 may receive the contents of either of the tanks 101 and may deliver its contents into either of the tanks 106, and so that the contents of either of the latter may be run into the filter-press 107.

The tanks 101 and 106 and the lime-mixer V are or may be constructed like the lime-mixer S (see Fig. 19) and the lime-tank \V like that represented by S, Fig. 19. The clear purified brine is pumped into the supply-tank 108, whence it is supplied to the ditferent apparatus. About ninety per cent. is run through the pipe a, the column tanks A A A Fig. 1, where it takes up ammonia from the gases that escape from the carbonating or precipitating apparatus, Fig. 6, and enter the column-tanks by way of the pipe a. From the columntanks it is pumped into the tank which supplies the saturator. It passes successively through thesaturator-col n mm B and saturator Fig. 2, and the salt-column C, Fig. 5, into i the averaging-tanks 109. The remaining ten per cent. of the purified brine is used in the square tower 110 to wash and recover ammonia from the gases which pass from the carbonating or precipitating apparatus D through the column-tanks A A A, and'enter the base of said tower by the pipe a. The waslrbrine is pumped up through the pipe 111 into the supplytank 112, whence it is delivered by the pipes 113 and 114, and is pumped into the ammoniated brine from the saturator in its averaging-tanks 109. In case the whole of the wash-brine is not required for diluting the ammoniated brine from the saturator, the excess is delivered by the pipes 113 and 115 into the brine from the column tank A on its way to the saturatorcolumn. Should the washbrine be insnfficient in quantity for the purpose named, frcshbrine from the supply-tank is added to the ammoniated brine, the said fresh brine being carried by the pipes 115 and 114 around the saturatorcolumn B saturator B, and salt-column C, and delivered into the averaging-tanks 109. At 116 one or more cocks are placed, so that either of the pipes 114 and 115 may be connected with the pipe 113, and so that they may also, when desired, be connected with each other. By turning the proper cooks the delivery of wash-brine or of fresh brine into the ammoniated brine can be regulatedj From the averaging tanks the brine is pumped through the pipe d into the carbonating or precipitating apparatus D, Fig. 6, where it meets the carbonic acid from the limekiln, Fig. 9, after passing through the compressor, the grainers, and the condenser, Fig. 12, and also the carbonic acid from the roaster M, Fig. 16, after passing through the dust-trap N,Fig. 16, acompressor, 117, anda surface-eondenser, 118. The gases from the carbonating or precipitating apparatus pass, as already stated, to and through the columntanks, Fig. 1, and the square tower. From the carbonating or precipitating apparatus the ammoniumchloride solution, holding the precipitated bicarbonate of soda in suspension, flows into the filter K Fig. 13, wherein the said solution is separated from the bicarbonate, and the latter is washed. The air drawn from the tank below the filter-belt through the pipe k into the aspirator and compressor K is by the latter forced into the iron-tower 119, where it is washed with water supplied from the tank 103 by the pipe 121. The wash-liquid is delivered through the pipe 122 into the ammoniumchloride solution from the filter K, having run through the pipe 7c, and its branchesinto the spider-tank 120, and thence into the receivingtank 124, is from the latter pumped or forced by steam acting upon the surface of the liquid, asina monte-j us, into thetank 123. The waste gases from the saturator-column B are conducted by the pipe 1) into the pipe-tower B, where'they are washed with water, which is run from the watertank 125 into the top of the said tower. The waste water is deliveredinto the ammonium-chloride tank 123 through the pipe I). The dust-trap is supplied with water from the tank 103 by the pipe at. The overilow by the pipe n and the water of condensation from the surface-condenser 118 are delivered by the pipe 126 into the tank 123. These ammoniated liquors are run from the tank 123, through the vpipe 129, condensercoluinn Q pipe a, lime tank S, pipe q, stillcolumns Q Q,into the boilers R R. 'Theammonia expelled from the solution in the still-columns and boiler, together with other vapors, pass by pipe 1 into condenser-column Q", and thence into condenser Q The cooled ammonia from the condenser unites with the ammonia from still Y, and by pipe 101 is delivered into the saturator. The calcium chloride solution which collects in the boilers R R is blown oli' from time to time. From the filter K the bicarbonate of soda is delivered by the belt-com veyer L into the roaster M, Fig. 16, wherein the extra equivalent of carbonic acid, together with the ammonia and moisture, are driven off, the said gases passing, as already stated, through the dust-trap N, compressor 117, and

that they all can be seen. 1

surface-condenser 118 to the carbonating or precipitating apparatus D. The sodium carbonate from the roaster is, by the elevator I? and jacketed conveyer P, (shown in Fig. 18,) conveyed to a packing-machine, 127, and is cooled in its passage.

The calcium chloride solution which is blown off from the still, Fig.19, is allowed to run to waste, or it can be utilized in any h nown and suitable way.

The pipes connected with each boiler are placed centrally on the boiler, one behind the other. In Fig. 19 their position is altered, so

Modifications can be made in the details without departing from the spirit of the invention, and parts of the invention can be used without the others.- For example, as follows:

Instead of using compressors and aspirators operating by means of steam jets on the principle of the injector for compressing the carbonic acid and forcreating a vacuum in thepipe-tower and in the filter-tank, pumps or other means of compression and aspiration could be used. The steam-jet devices have, however, special advantages in the connection in which they are employed, and their use in such connection of them in contradistinction to other compressors and aspirators forms a part of the invention.

Instead of using the brine for soda making as .a washliquid to recover the ammonia, water could be employed, the wash-water to be afterward distilled; but it is obvious that in such cases the advantages attending the use In the saturator other than scoop-shaped paddles could be used, although it is believed that the scoop-paddles are best adapted to the purpose. A similar remark applies to the roaster, only in that case, owing to the peculiar nature of the material to be roasted, there are greater difficulties in ,the way of a change. The zigzag arrangement of fiues shown in Fig. 8 could be adopted in the saturator and'roaster, as well as in the carbonating or precipitating apparatus. The brine could be passed through the salt'column after instead of before the brine is corrected for ammonia. V

The saturator could be used to absorb ammonia obtained from any available source, or

. it'might be used for other purposes, and so of other apparatus. One or more of the apparatuseould be substituted for corresponding apparatus in existing systems with improvement to the latter; but it is obvious in such case a part only of theinvention would be our ployed.

Many other changes and modifications could be indicated; but it is believed to be unnecessary, what has been described being considered the best mode of carrying the invention 

